# useDeferredValue + memo

<EpicVideo url="https://www.epicreact.dev/workshops/react-performance/usedeferredvalue-and-memo" />

👨‍💼 We've got a performance problem with our `Card` component in this UI. (🧝‍♂️
actually, I just added an arbitrary slowdown to simulate a problem to keep this
exercise simple while still teaching the lesson). As a result, every time we
type in the `search` the characters are not responsive.

You might think that you can get away with just adding `memo` around the `Card`
and we absolutely want you to do that, but once you try, you'll notice that
typing a bunch in the search and then clearing the search is still a really slow
experience. We need concurrent rendering!

So please `memo`-ize the `Card` component, and add `useDeferredValue` to the
`query` you use to filter the cards and check the performance difference.
